I. Field of the Invention
The present invention relates generally to the field of catheters. More particularly it relates to guiding catheters having torque transmittal guidance walls that are flexible linearly but not circumferentially and that are neither collapsible nor kinkable. It is particularly suited as a vascular catheter.
II. Description of the Prior Art
Vascular catheters and some other types of catheters requiring remote guidance of insertion from outside of a patient have fine spiralled or braided metallic or non-metallic strands of reinforcement material in thin cylindrical walls of flexible catheter tubing. The catheter body must (a) contain fluid pressures up to 1,000 psi, (b) transmit rotational torque accurately from a proximal end outside of a patient to a distal end inside of the patient, (c) prevent collapse, kinking or alteration of conveyance area of the catheter, (d) convey electrical current or sound wave energy from end-to-end of the catheter and yet, (e) flex sufficiently not to injure bodily tissues. Diagnostic instrumentation, traceable fluids, medicine and body fluids must be conveyed through the catheter lumen effectively. Total diameter of the catheter tubing, however, is often less than one-tenth of an inch.
Guidance of such catheters within vascular and other body channels is achieved usually by selectively slight rotation of the catheter with a small handle at the proximal end. At the distal end near a non-injurious tip of the catheter inside of the patient, there is generally a curved directional bend. The slight rotation of the catheter points this directional bend precisely in a desired circumferential direction at a particular position of confluence or other physical condition of the body lumens or channels. This directs or guides insertional advancement of the catheter into desired body channels or lumens. Other guidance means employ unbent catheters in combination with various steerable tips.
A variety of problems have occurred with these small guiding catheters and related components previously. One problem has been a tendency of reinforcement strands to separate from polymer or various flexible materials from which the body of the catheter tubing is constructed. This destroys rotational torque transmittal capacity and leaves the catheter subject to kinking, collapse and general failure of its design requirements.
Another problem has been insufficient lubricity of inside catheter walls for conveyance of instrumentation, liquids and slurries of diagnostic and medicinal materials with low viscosity. Outside walls of catheters also have had inadequate lubricity for passage in and out of relatively small body channels.
Another problem has been inadequately resilient directional bends at distal ends of catheters. Some have been too rigid. Others have been the opposite without sufficient resilience memory to regain a directional curve after being straightened or bent differently in various portions of body channels.
A relatively common problem has been incapacity of a catheter having sufficient linear flexibility to convey rotational torque between a reinforced catheter body and a desirably flexible or soft catheter tip.
Still another problem has been incapacity of previous catheters to be drilled or welded to form side apertures referred to as perfusion ports. The walls of present catheters delaminate, separate and fail from heat of either drilling or welding.
Solving these and other problems has inspired this invention.
Different but pertinent catheter technology is described in the following patent documents.
______________________________________ NATION NUMBER DATE NAME ______________________________________ Euro. 0 421 650 A1 Apr. 10, 1991 Frassica U.S. 4,764,324 Aug. 16, 1988 Burnham U.S. 4,676,229 Jun. 30, 1987 Krasnicki et al U.S. 4,577,543 Mar. 25, 1986 Wilson U.S. 4,531,943 Jul. 30, 1985 Van Tassel et al U.S. 4,425,919 Jan. 17, 1984 Alston, Jr. et al U.S. 3,924,632 Dec. 9, 1975 Cook U.S. 3,498,286 Mar. 3, 1970 Polanyi et al ______________________________________
The Frassica European Patent taught rolled layers of polymeric film interspersed with reinforcement materials and various instrumentation elements. High versatility of construction was a main feature of that patent. A wide variety of features could be provided at various portions of the catheter body. Problems, however, were tendency of the layers to separate, large diameter, ridges at linear and circumferential joints and high production cost to achieve variations. Also different from this invention, it could not be customized by mere programming of most of its features into a production process.
The Burnham Patent taught a single extrusion method based on tensioning reinforcement strands being wound around heat softened thermoplastic catheter walls to draw the strands radially into the walls after they were formed. Different from this invention, however, it was not a process that applied catheter wall material inside and outside of the reinforcement strands during a simultaneous co-extrusion and strand winding process to form monolithic walls with tightly woven reinforcement strands. It had no solid lubrication in its walls. There was no wall interruption or channelling for friction reduction. Its reinforcement was not sufficiently variable linearly. There was no means for welding tips in close proximity to torque transmittal reinforcement strands to transmit torque effectively or to prevent tips from coming off inside of patients. Nor was there means for providing profusion ports and other features without destroying structural integrity of the catheter.
The Krasnicki et al Patent described an endoscope biopsy channel with a lubricous inner layer bounded by high strength wire helically wound around it. A soft outer layer provided protection against injury of tissue. Flexible material filled space between wire strands and between the lubricous inner wall and the soft outer wall. That catheter was not producible with sufficiently small diameters and thin walls. Separate walls inside and outside of helical windings consume too much space for small diameter production or for space efficient large diameter catheters.
The Wilson Patent taught a method to form what it referred to as a monolithic construction of cannulae that could be used for a catheter. Reinforcement strands were wound around the outside of a catheter tube that was then heated to cause the strands to adhere to the outside of the tube. In an optional subsequent step of the method, an additional layer of material was extruded onto the outside of the reinforcement strands. Unlike this invention, however, that method was not a simultaneous co-extrusion and wrapping process that formed a more integrated monolithic wall with less likelihood of separation. There was no solid lubricant at surfaces nor friction reduction channels between solid lubricant surfaces. There was no method for attaching integral tips nor providing profusion ports without destroying structural integrity.
The Van Tassel et al Patent taught the attachment of a soft balloon like tip to ends of catheters. But it was not a method that could be used for attachment to reinforced walls because it required step cutting of the catheter wall.
The Alston, Jr. et al Patent positioned flat wire braiding between layers of material. This required thick walls in proportion to diameter of catheters. Separation of the layers was problematic for thin walls with that type of construction. It was not a monolithic type of wall taught by this invention.
The Cook Patent employed conventional sandwiching of fiberglass woven roving between plastic layers of tubing. Walls were far too thick for the conveyance efficiency required for current medical practices.
The Polanyi et al Patent combined a wide variety of catheter features in a catheter wall. But the constructional form was far too thick and the cost of construction too high in comparison to present catheters. It was one of the first catheters to utilize fiber optics, but in forms that have been superseded with smaller and more efficient fiber optics and diagnostic equipment made possible with this invention. Its walls and linear components would separate if made sufficiently thin for current catheter applications.